U.S. patent number RE44,564 [Application Number 13/476,973] was granted by the patent office on 2013-10-29 for method for transmitting control signal using efficient multiplexing.
This patent grant is currently assigned to LG Electronics Inc.. The grantee listed for this patent is Joon Kui Ahn, Sung Duk Choi, Seong Hoon Jeong, Bong Hoe Kim, Hak Seong Kim, Ki Jun Kim, Jung Hoon Lee, Dong Youn Seo, Suk Hyon Yoon, Young Woo Yun. Invention is credited to Joon Kui Ahn, Sung Duk Choi, Seong Hoon Jeong, Bong Hoe Kim, Hak Seong Kim, Ki Jun Kim, Jung Hoon Lee, Dong Youn Seo, Suk Hyon Yoon, Young Woo Yun.
United States Patent |
RE44,564 |
Kim , et al. |
October 29, 2013 |
Method for transmitting control signal using efficient
multiplexing
Abstract
Methods of transmitting a control signal using efficient
multiplexing are disclosed. One of the method includes the steps of
multiplexing a plurality of 1-bit control signals within a
prescribed time-frequency domain by code division multiple access
(CDMA) and transmitting the multiplexed control signals, wherein a
plurality of the 1-bit control signals include a plurality of the
1-bit control signals for a specific transmitting side.
Accordingly, reliability on 1-bit control signal transmission can
be enhanced.
Inventors: |
Kim; Hak Seong (Anyang-si,
KR), Choi; Sung Duk (Anyang-si, KR), Kim;
Ki Jun (Anyang-si, KR), Yoon; Suk Hyon
(Anyang-si, KR), Ahn; Joon Kui (Anyang-si,
KR), Kim; Bong Hoe (Anyang-si, KR), Seo;
Dong Youn (Anyang-si, KR), Yun; Young Woo
(Anyang-si, KR), Lee; Jung Hoon (Anyang-si,
KR), Jeong; Seong Hoon (Anyang-si, KR) |
Applicant: |
Name |
City |
State |
Country |
Type |
Kim; Hak Seong
Choi; Sung Duk
Kim; Ki Jun
Yoon; Suk Hyon
Ahn; Joon Kui
Kim; Bong Hoe
Seo; Dong Youn
Yun; Young Woo
Lee; Jung Hoon
Jeong; Seong Hoon |
Anyang-si
Anyang-si
Anyang-si
Anyang-si
Anyang-si
Anyang-si
Anyang-si
Anyang-si
Anyang-si
Anyang-si |
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A |
KR
KR
KR
KR
KR
KR
KR
KR
KR
KR |
|
|
Assignee: |
LG Electronics Inc. (Seoul,
KR)
|
Family
ID: |
39268894 |
Appl.
No.: |
13/476,973 |
Filed: |
May 21, 2012 |
PCT
Filed: |
October 02, 2007 |
PCT No.: |
PCT/KR2007/004825 |
371(c)(1),(2),(4) Date: |
April 02, 2009 |
PCT
Pub. No.: |
WO2008/041820 |
PCT
Pub. Date: |
April 10, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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60955019 |
Aug 9, 2007 |
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60827852 |
Oct 2, 2006 |
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Reissue of: |
12444100 |
Oct 2, 2007 |
7953061 |
May 31, 2011 |
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Foreign Application Priority Data
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Feb 5, 2007 [KR] |
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10-2007-0011533 |
Oct 2, 2007 [KR] |
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10-2007-0099055 |
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Current U.S.
Class: |
370/342;
370/479 |
Current CPC
Class: |
H04L
5/0007 (20130101); H04L 1/1858 (20130101); H04L
1/1607 (20130101); H04L 5/0053 (20130101); H04L
1/1861 (20130101); H04W 72/0446 (20130101); H04L
5/0055 (20130101); H04L 1/1854 (20130101); H04W
72/0453 (20130101); H04W 88/02 (20130101); H04L
5/0026 (20130101); H04W 88/08 (20130101) |
Current International
Class: |
H04B
7/216 (20060101) |
References Cited
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Primary Examiner: Harper; Kevin C
Attorney, Agent or Firm: Lee, Hong, Degerman, Kang &
Waimey
Parent Case Text
.Iadd.CROSS-REFERENCE TO RELATED APPLICATIONS.Iaddend.
.Iadd.This application is a reissue of U.S. Pat. No. 7,953,061,
which issued on May 31, 2011, from U.S. application Ser. No.
12/444,100, filed on Apr. 2, 2009, which is the National Stage
filing under 35 U.S.C. 371 of International Application No.
PCT/KR2007/004825, filed on Oct. 2, 2007, which claims the benefit
of earlier filing date and right of priority to Korean Application
Nos. 10-2007-0011533, filed on Feb. 5, 2007 and 10-2007-0099055,
filed on Oct. 2, 2007, and also claims the benefit of U.S.
Provisional Application Ser. Nos. 60/827,852, filed on Oct. 2,
2006, and 60/955,019, filed on Aug. 9, 2007..Iaddend.
Claims
What is claimed is:
1. A method of transmitting a control signal, the method
comprising: multiplexing a plurality of 1-bit control signals
within a single prescribed time-frequency domain by a code division
multiple access (CDMA) scheme, wherein the plurality of 1-bit
control signals multiplexed within the single prescribed
time-frequency domain are distinguished by orthogonal or
pseudo-orthogonal codes used for multiplexing each of the plurality
of 1-bit control signals; repeating multiplexing of the plurality
of multiplexed control signals in different frequency domains; and
transmitting the repeatedly multiplexed control signals.
2. The method of claim 1, wherein when a time domain used for the
control signal transmission comprises a single OFDM symbol zone,
the repeating comprises repeatedly multiplexing the multiplexed
control signals in the different frequency domains within the
single OFDM symbol zone.
3. The method of claim 1, wherein when a time domain used for the
control signal transmission comprises a plurality of OFDM symbol
zones, the repeating comprises repeatedly multiplexing the
multiplexed control signals in the different frequency domains
within the plurality of OFDM symbol zones that are different from
each other.
4. The method of claim 1, wherein in the multiplexing, the
plurality of 1-bit control signals are further distinguished by
different orthogonal phase components.
5. A method of transmitting a control signal, the method
comprising: multiplexing a plurality of 1-bit control signals
within a single prescribed time-frequency domain by a code division
multiple access (CDMA) scheme; multiplexing the multiplexed
plurality of 1-bit control signals by at least a time division
multiple access (TDMA) scheme or a frequency division multiple
access (FDMA) scheme such that the multiplexing of the plurality of
1-bit control signals is repeated within an additional
time-frequency domain other than the single prescribed
time-frequency domain; and transmitting the multiplexed control
signals.
6. The method of claim 5, wherein the plurality of 1-bit control
signals for different transmitting sides are multiplexed within the
single prescribed time-frequency domain and the additional
time-frequency domain by the CDMA scheme, respectively.
7. The method of claim 5, wherein a 1-bit control signal for a
specific transmitting side is multiplexed with other 1-bit control
signals using orthogonal or pseudo-orthogonal codes that are
different from each other, the method further comprising: repeating
the multiplexing of the 1-bit control signal for the specific
transmitting side within the additional time-frequency domain other
than the single prescribed time-frequency domain; and transmitting
the repeatedly multiplexed 1-bit control signal for the specific
transmitting side.
8. The method of claim 7, wherein the orthogonal or
pseudo-orthogonal codes comprise a code sequence having a length
corresponding to a size of the single prescribed time-frequency
domain.
9. The method of claim 1, wherein the plurality of 1-bit control
signals comprise ACK/NACK signals.
10. The method of claim 5, wherein the plurality of 1-bit control
signals comprise ACK/NACK signals.
Description
TECHNICAL FIELD
The present invention relates to a method for transmitting a
control signal in a multi-carrier mobile communication system, and
more particularly, to a control signal transmitting method.
Although the present invention is suitable for a wide scope of
applications, it is particularly suitable for transmitting a
control signal reliably in uplink/downlink transmission by
multiplexing a plurality of 1-bit control signals efficiently.
BACKGROUND ART
Generally, in a multi-carrier mobile communication system, a base
station performs downlink data packet transmission to user
equipments (hereinafter abbreviated UEs) belonging to a cell or
each of a plurality of cells. Meanwhile, a plurality of UEs may
exist within a cell. Since each of the UEs is unable to know how a
data packet will be transmitted to itself using a prescribed
format, when a base station transmits a downlink data packet to a
specific UE, the base station should transmit such necessary
information as an ID of a UE that will receive the corresponding
data packet, a time-frequency domain for carrying the data packet,
a data transmission format including a coding rate, a modulation
scheme and the like, HARQ relevant information, and the like in
downlink for each downlink data packet transmission.
On the contrary, in order to enable a UE to transmit a data packet
in uplink, a base station should transmit such necessary
information as an ID of a UE that will be approved for data packet
transmission, an uplink time-frequency domain enabling the UE to
transmit the data packet, a data transmission format including a
coding rate, a modulation scheme and the like, HARQ relevant
information, and the like in downlink for each uplink data packet
transmission.
In case of the uplink data packet transmission, a base station
should transmit reception success
acknowledgement/non-acknowledgement (ACK/NACK) information on each
data having been transmitted by a UE to the corresponding UE in
uplink. On the other hand, in case of downlink data packet
transmission, each UE transmits information about reception success
or failure for each data packet having been transmitted by a base
station through ACK/NACK information in uplink.
In order to maintain an uplink transmission/reception power of each
UE at a proper level, a base station should transmit power control
information to each UE in downlink.
Among the above-explained control signals, an ACK/NACK signal, a
power control signal or the like is mainly able to indicate the
corresponding information using one bit and can be named `1-bit
control signal`.
In order to operate and manage a system efficiently, it is
necessary to multiplex an uplink/downlink control signal for
carrying the above-explained control information, and more
particularly, the 1-bit control signal with a data packet and other
signals in a time-frequency resource efficiently.
As a multiplexing scheme normally used for a multi-carrier mobile
communication system, time division multiple access (TDMA) for
multiplexing a plurality of signals by dividing them on a time
domain, frequency division multiple access (FDMA) for multiplexing
a plurality of signals by dividing them on a frequency domain, code
division multiple access (CDMA) for multiplexing signals on a
prescribed time-frequency domain using an orthogonal code or a
pseudo-orthogonal code, or the like can be used.
Yet, in case that the 1-bit control signal is multiplexed using
TDMA and/or FDMA only, since a transmission power of each control
signal considerably differs, an effect on a neighbor cell may
differ on a time domain and/or a frequency domain.
In particular, when a random cell multiplexes to transmit ACK/NACK
signals for different UEs within a single TTI by TDMA or FDMA for
example, in case that an ACK/NACK signal transmission power for
each of the UEs considerably differs, a quantity of interference
imposed on neighbor cells by the corresponding cell may differ
considerably on a time domain or a frequency domain. And, this may
have a bad influence on performing downlink data packet scheduling
in a cellular environment or time-frequency-energy distributions
efficiently.
Moreover, in case that a control signal such as an ACK/NACK signal
of a transmitting side is lost in the course of downlink/uplink
channel transmission, there may be a problem of reliability on the
corresponding signal transmission.
DISCLOSURE OF THE INVENTION
Technical Problem
Technical Solution
Accordingly, the present invention is directed to a method for
transmitting a control signal in a multi-carrier mobile
communication system that substantially obviates one or more of the
problems due to limitations and disadvantages of the related
art.
An object of the present invention is to provide a method of
transmitting a plurality of control signals efficiently, by which a
control signal of a specific transmitting side can be reliably
transmitted in a manner of performing multiplexing efficiently to
minimize inter-cell interference in control signal
transmission.
Additional features and advantages of the invention will be set
forth in the description which follows, and in part will be
apparent from the description, or may be learned by practice of the
invention. The objectives and other advantages of the invention
will be realized and attained by the structure particularly pointed
out in the written description and claims thereof as well as the
appended drawings.
To achieve these and other advantages and in accordance with the
purpose of the present invention, as embodied and broadly
described, a method of transmitting a control signal according to
the present invention includes multiplexing a plurality of 1-bit
control signals within a prescribed time-frequency domain by code
division multiple access (CDMA), repeating the multiplexed control
signals in different frequency domains, and transmitting the
repeated control signals.
To achieve these and other advantages and in accordance with the
purpose of the present invention, as embodied and broadly
described, a method of transmitting a control signal according to
the present invention includes multiplexing a plurality of 1-bit
control signals within a prescribed time-frequency domain by code
division multiple access (CDMA), and transmitting the multiplexed
control signals, wherein a plurality of the 1-bit control signals
include a plurality of the 1-bit control signals for a specific
transmitting side.
Preferably, wherein the prescribed time-frequency domain comprises
a time-frequency domain within 1 OFDM symbol zone.
Preferably, wherein in case that a time domain used for the control
signal transmission comprises a single OFDM symbol zone, the
repeating is carried out in a manner of repeating the multiplexed
control signals into the different frequency domains within the
single OFDM symbol zone.
Preferably, wherein in case that a time domain used for the control
signal transmission comprises a plurality of OFDM symbol zones, the
repeating is carried out in a manner of repeating the multiplexed
control signals into the different frequency domains within the
OFDM symbol zones differing from each other.
Preferably, in the multiplexing, a plurality of the 1-bit control
signals are discriminated by an orthogonal or pseudo-orthogonal
code used for multiplexing of each of the 1-bit control
signals.
More preferably, a plurality of the 1-bit control signals are
modulated by being discriminated by different orthogonal phase
components, respectively and wherein in the multiplexing, a
plurality of the 1-bit control signals are additionally
discriminated by the different orthogonal phase components used for
the modulation.
Preferably, the prescribed time-frequency domain includes a
plurality of time-frequency domains. In the multiplexing,
additional multiplexing is carried out by at least one selected
from the group consisting of time division multiple access (TDMA)
and frequency division multiple access (FDMA). And, a plurality of
the 1-bit control signals for the specific transmitting side are
multiplexed by being spread in a plurality of the time-frequency
domains.
More preferably, the 1-bit control signals for different
transmitting sides are multiplexed in a plurality of the
time-frequency domains by the code division multiple access,
respectively. In this case, a plurality of the 1-bit control
signals for the specific transmitting side are multiplexed by
different orthogonal or pseudo-orthogonal codes.
And, the orthogonal or pseudo-orthogonal code includes a code
sequence having a length corresponding to a size of a plurality of
the time-frequency domains.
Besides, the 1-bit control signal can include either an ACK/NACK
signal or a power control signal. And, the 1-bit control signal can
be transmitted in either uplink or downlink.
It is to be understood that both the foregoing general description
and the following detailed description are exemplary and
explanatory and are intended to provide further explanation of the
invention as claimed.
ADVANTAGEOUS EFFECTS
According to one embodiment of the present invention, in
multiplexing a plurality of 1-bit control signals, CDMA is mainly
used. And, it is able to transmit a plurality of controls signals
of a specific UE through different orthogonal or pseudo-orthogonal
codes, respectively. Hence, it is able to enhance reliability on
the corresponding control signal transmission.
And, the number of multiplexed signals in coherence bandwidth
and/or coherence time can be increased by carrying out FDMA and/or
TDMA on the 1-bit control signal transmission side by side and by
distributing to transmit a plurality of control signals for a
specific UE on each time-frequency domain.
Moreover, in case of transmitting the 1-bit control signal through
a plurality of time-frequency domains, by specifying to use an
orthogonal code used for transmission in accordance with the size
the whole time-frequency domains instead of the size of each the
time-frequency domain, it is able to increment a number of control
signals that can be simultaneously transmitted.
Besides, in case that a plurality of OFDM symbols are used for
1-bit control signal transmission, by transmitting a CDMA modulated
1-bit control signal on a different OFDM symbol area through a
different frequency domain, it is able to perform efficient
transmission in aspects of resource efficiency and diversity gain.
And, it is also able to make a power allocation more flexible
within each OFDM symbol area.
DESCRIPTION OF DRAWINGS
The accompanying drawings, which are included to provide a further
understanding of the invention and are incorporated in and
constitute a part of this specification, illustrate embodiments of
the invention and together with the description serve to explain
the principles of the invention.
In the drawings:
FIG. 1 is a diagram for explaining a method of multiplexing to
transmit ACK/NACK signals by CDMA according to one embodiment of
the present invention;
FIG. 2 is a diagram for explaining a method of transmitting
ACK/NACK signals by carrying out multiplexing side by side with
CDMA and FDMA according to one embodiment of the present
invention;
FIG. 3 is a diagram for explaining a method of transmitting
ACK/NACK signals by carrying out multiplexing side by side with
CDMA, TDMA and FDMA according to one embodiment of the present
invention;
FIG. 4 is a diagram for explaining a method of transmitting
ACK/NACK signals by carrying out multiplexing side by side with
CDMA and FDMA according to one embodiment of the present invention,
in which a plurality of ACK/NACK signals transmitted by a specific
transmitting side among a plurality of ACK/NACK signals are
transmitted through a plurality of frequency domains;
FIG. 5 is a diagram for explaining a method of transmitting
ACK/NACK signals by carrying out multiplexing side by side with
CDMA, TDMA and FDMA according to one embodiment of the present
invention, in which a plurality of ACK/NACK signals transmitted by
a specific transmitting side among a plurality of ACK/NACK signals
are transmitted through a plurality of time-frequency domains;
FIG. 6 is a diagram for explaining a method of transmitting
ACK/NACK in case of using 1 OFDM symbol zone for ACK/NACK
transmission according to one embodiment of the present
invention;
FIG. 7 is a diagram for explaining a method of transmitting
ACK/NACK in case of using at least 2 OFDM symbol zones for ACK/NACK
transmission according to one embodiment of the present
invention;
FIG. 8 is a diagram for explaining a method of transmitting
ACK/NACK in case of using at least 2 OFDM symbol zones for ACK/NACK
transmission according to one preferred embodiment of the present
invention; and
FIG. 9 is a diagram to explain a principle that power allocation
flexibility is increased in case of transmitting ACK/NACK signals
by the embodiment shown in FIG. 8.
BEST MODE
Mode for Invention
Reference will now be made in detail to the preferred embodiments
of the present invention, examples of which are illustrated in the
accompanying drawings.
Generally, a base station transmits an ACK/NACK signal indicating a
success or failure in receiving a data packet transmitted by each
UE within a cell or a control signal playing a role similar to that
of the ACK/NACK signal to the corresponding UE in downlink. In
doing so, since a plurality of UEs are able to transmit uplink data
packets within a single TTI, the base station is able to transmit
ACK/NACK signals to a plurality of the UEs within a single TTI as
well.
And, a base station multiplexes a plurality of power control
signals for controlling transmission powers of uplink data of a
plurality of UEs for a single TTI within a cell and then transmits
the multiplexed signal to each of the UEs.
Hence, according to one embodiment of the present invention, in
order to multiplex and transmit a plurality of 1-bit control
signals efficiently, a method of multiplexing to transmit a
plurality of 1-bit control signals by CDMA within a partial
time-frequency domain of a transmission band in a multi-carrier
system is proposed. And, this will be explained with reference to a
detailed example.
Meanwhile, the description for one embodiment of the present
invention relates to a case that a 1-bit control signal is an
ACK/NACK signal for example. In a control signal transmitting
method according to one embodiment of the present invention, a
1-bit control signal needs not to be an ACK/NACK signal
necessarily. And, it is apparent to those skilled in the art that
the present invention includes a random 1-bit control signal in a
format that a plurality of signals are transmitted within 1
TTI.
FIG. 1 is a diagram for explaining a method of multiplexing to
transmit ACK/NACK signals by CDMA according to one embodiment of
the present invention.
Referring to FIG. 1, according to one embodiment of the present
invention, a base station reserves a specific time-frequency domain
within 1 TTI for ACK/NACK transmission to use. And, ACK/NACK
signals for different UEs are discriminated from each other by an
orthogonal or pseudo-orthogonal code multiplied on a time-frequency
domain.
In this case, the `orthogonal code` or the `pseudo-orthogonal code`
is a code used for signal multiplexing in CDMA and means a code
that indicates that a correlation is 0 or a value smaller than a
prescribed threshold.
According to one preferred embodiment of the present invention, in
case of performing a transmission through modulation that uses
components having phases orthogonal to each other like QPSK, a
plurality of ACK/NACK signals can be additionally discriminated
through the different orthogonal phase components.
In an example shown in FIG. 1, since an ACK/NACK signal is
transmitted through a time-frequency domain including 12
subcarriers across six OFDM symbols within a single TTI, it is able
to use an orthogonal code having a chip length 72 (=6.times.12) for
the ACK/NACK transmission.
Hence, it is possible to simultaneously transmit 72 different
orthogonal signals. Yet, a number of simultaneously transmittable
orthogonal signals may vary in accordance with a type of a used
orthogonal/pseudo-orthogonal code.
In case of using QPSK as a modulation scheme in the example shown
in FIG. 1, it is able to use two orthogonal phases. Hence, it is
able to transmit different orthogonal signals amounting to a double
of the seventy-two orthogonal signals.
Meanwhile, an ACK/NACK signal for a single UE can be transmitted
via a single orthogonal signal among the orthogonal signals
generated by the above-explained method. Yet, one embodiment of the
present invention proposes that an ACK/NACK signal for a single UE
is set to be transmitted via a plurality of orthogonal signals if
the single ACK/NACK signal carries information exceeding 1 bit or
if a single UE transmits a plurality of data packets for a single
TTI.
Like the above-explained one embodiment of the present invention,
an advantage in multiplexing to transmit an ACK/NACK signal by CDMA
in downlink lies in that a quantity of interference generated in
downlink by an ACK/NACK signal on a time-frequency domain of a
single TTI can be maintained relatively equal.
In particular, if a random cell multiplexes to transmit ACK/NACK
signals for different UEs by TDMA or FDMA within a single TTI, as
mentioned in the foregoing description, if ACK/NACK signal
transmission powers for the respective UEs considerably differ from
each other, an interference quantity having influence on neighbor
cells by the corresponding cell can vary on a time domain or a
frequency domain considerably. And, this may have bad influence on
performing downlink data packet scheduling or other
time-frequency-energy distribution in a cellular environment. Yet,
in case that an ACK/NACK signal is multiplexed by CDMA like one
embodiment of the present invention, even if different ACK/NACK
signal transmission powers are allocated to different UEs, ACK/NACK
signals for the entire UEs are added together within a same
time-frequency domain for a single TTI and then transmitted. Hence,
fluctuation of transmission power on a time-frequency domain can be
minimized.
Like one embodiment of the present invention, in case that a
plurality of ACK/NACK signals transmitted by a single UE or for
data transmission of a single UE are transmitted via a plurality of
orthogonal signals, it is able to enhance reliability of ACK/NACK
signal transmission to the corresponding UE.
Moreover, the above-explained principle for the downlink
transmission of the ACK/NACK signal is identically applicable to
uplink transmission.
Meanwhile, in multiplexing ACK/NACK signal by CDMA, as mentioned in
the foregoing description, orthogonality between the different
ACK/NACK signals multiplexed by CDMA can be maintained only if a
downlink radio channel response characteristic is not considerably
changed on a time-frequency domain for carrying the ACK/NACK
signal. Hence, it is able to obtain satisfactory reception
performance without applying a special reception algorithm such as
a channel equalizer in a receiving end. Preferably, CDMA
multiplexing of ACK/NACK signal is carried out within a
time-frequency domain, in which a radio channel response is not
considerably changed, i.e., within a coherent time and a coherent
bandwidth.
According to a detailed embodiment of the present invention, a CDMA
multiplexing scheme of ACK/NACK signal can be carried out side by
side with a FDMA or TDMA multiplexing scheme to narrow a
time-frequency domain for multiplexing ACK/NACK signal by CDMA
within a coherent range in which a radio channel response
characteristic is not considerably changed. This is explained as
follows.
FIG. 2 is a diagram for explaining a method of transmitting
ACK/NACK signals by carrying out multiplexing side by side with
CDMA and FDMA according to one embodiment of the present
invention.
Referring to FIG. 2, different ACK/NACK signals can be transmitted
in time-frequency domains separated from each other on two
frequency axes. And, different ACK/NACK signals can be multiplexed
by CDMA in each of the time-frequency domains. In this case,
according to one embodiment of the present invention, as ACK/NACK
signals are transmitted through two frequency domains, it can be
observed that a width of each of the frequency domains is set to a
6-subcarrier zone narrower than a 12-subcarrier zone.
In particular, in the example shown in FIG. 2, since each of the
two time-frequency domains includes six OFDM symbols and twelve
subcarriers, it is able to transmit 36 (=6.times.6) orthogonal
signals by CDMA. Since two time-frequency domains are used within a
single TTI, it is able to transmit 72 (=36.times.2) orthogonal
signals.
In case that QPSK modulation is used, since ACK/NACK signal can be
additionally discriminated using two orthogonal phases, it is able
to transmit different orthogonal signals amounting to two times of
the 72 orthogonal signals.
FIG. 3 is a diagram for explaining a method of transmitting
ACK/NACK signals by carrying out multiplexing side by side with
CDMA, TDMA and FDMA according to one embodiment of the present
invention.
In particular, FIG. 3 shows an example that multiplexing is carried
out on ACK/NACK signals side by side with CDMA, FDMA and TDMA.
Referring to FIG. 3, different ACK/NACK signals can be transmitted
on four time-frequency domains having less channel variations. And,
different ACK/NACK signals can be multiplexed in each of the
time-frequency domains by CDMA.
In particular, in the example shown in FIG. 3, since each of the
time-frequency domains includes three OFDM symbols and six
subcarriers, it is able to transmit 18 (=3.times.6) ACK/NACK
signals in each domain by CDMA. Since four time-frequency domains
are used within a single TTI, it is also able to transmit 72
(=18.times.4) ACK/NACK signals. Since two orthogonal phases are
usable for QPSK transmission, it is able to transmit a double of
the different ACK/NACK signals.
In the above-explained ACK/NACK signal multiplexing scheme shown in
FIG. 2 or FIG. 3, the scheme for transmitting the different
ACK/NACK signals in each of the time-frequency domains is more
advantageous than that of FIG. 1 in that each of the ACK/NACK
signals can be transmitted within the time-frequency domain having
not considerable fluctuation of the radio channel response
characteristic. Yet, in case that a radio channel quality for a
prescribed UE in the time-frequency domain for carrying the
ACK/NACK signals is poor, ACK/NACK reception performance of the
corresponding UE can be considerably degraded.
Hence, one embodiment of the present invention proposes that
ACK/NACK signals for a specific UE within a single TTI are
transmitted across time-frequency domains distant from a plurality
of time-frequency axes. And, one embodiment of the present
invention also proposes a scheme for obtaining a time-frequency
diversity gain for ACK/NACK signal reception in a receiving end by
multiplexing ACK/NACK signals for different UEs by CDMA in each
time-frequency domain.
FIG. 4 is a diagram for explaining a method of transmitting
ACK/NACK signals by carrying out multiplexing side by side with
CDMA and FDMA according to one embodiment of the present invention,
in which a plurality of ACK/NACK signals transmitted by a specific
transmitting side among a plurality of ACK/NACK signals are
transmitted through a plurality of frequency domains.
Referring to FIG. 4, a receiving side is able to obtain a frequency
diversity gain in a manner that an ACK/NACK signal is transmitted
across two different frequency domains. In the example shown in
FIG. 4, an ACK/NACK signal is transmitted across two time-frequency
domains and different ACK/NACK signals are multiplexed in each of
the time-frequency domains.
In particular, since each of the time-frequency domains includes
six OFDM symbols and six subcarriers, there exist 36 (6.times.6)
ACK/NACK signals that can be multiplexed by CDMA in each of the
time-frequency domains. Since two orthogonal phases are usable for
QPSK transmission, it is able to transmit a double of the different
ACK/NACK signals.
As mentioned in the foregoing description, in multiplexing
different ACK/NACK signals within each of the time-frequency
domains using an orthogonal code regulated in accordance with the
size of each time-frequency domain, ACK/NACK signals transmitted
via different time-frequency domains for a specific UE can be
multiplexed using the same orthogonal code among orthogonal codes
used for each of the time-frequency domains.
Yet, one embodiment of the present invention proposes that ACK/NACK
signals transmitted via different time-frequency domains for a
specific UE are multiplexed using different orthogonal codes among
orthogonal codes used for each of the time-frequency domains.
Thus, in case that ACK/NACK signals for a specific UE are
multiplexed using different orthogonal codes in each domain, it is
able to prevent reception performance from being reduced by special
orthogonality reduction influence with other ACK/NACK signals with
which a specific ACK/NACK signal is CDMA multiplexed for a specific
TTI. And, this scheme can be extended to enable ACK/NACK signal of
a specific UE to be transmitted using different orthogonal codes in
different time-frequency domains even if the ACK/NACK signal is
transmitted via at least three time-frequency domains.
In case that ACK/NACK signals are transmitted via a plurality of
time-frequency domains, as shown in FIG. 4, one preferred
embodiment of the present invention proposes that more ACK/NACK
signals can be simultaneously transmitted in a manner of specifying
orthogonal codes in accordance with the size of the entire domains
instead of specifying an orthogonal code in accordance with in the
size of each the time-frequency domain and then transmitting a
plurality of ACK/NACK signals correspondingly.
In particular, in the example shown in FIG. 4, by obtaining 72
orthogonal codes in accordance with 72 (=6.times.12) chip length
according to six OFDM symbols and 12 subcarriers belonging to two
time-frequency domains for carrying a plurality of ACK/NACK signals
of a specific UE instead of 36 chip length according to six OFDM
symbols and six subcarriers belonging to a single time-frequency
domain, it is able to simultaneously transmit 144 ACK/NACK signals
using different orthogonal phases in case of using QPSK
transmission.
In this case, a problem generated from a fact that orthogonality
between orthogonal codes is reduced due to a considerable
difference between radio channel responses of different
time-frequency domains can be overcome by allocating ACK/NACK
transmission powers differing from each other in accordance with
partial cross correlation characteristics between orthogonal
codes.
In particular, if transmission powers of orthogonal codes within a
corresponding group are matched by grouping codes decided as having
low orthogonality among the above-specified orthogonal codes, the
above orthogonality problem can be solved.
FIG. 5 is a diagram for explaining a method of transmitting
ACK/NACK signals by carrying out multiplexing side by side with
CDMA, TDMA and FDMA according to one embodiment of the present
invention, in which a plurality of ACK/NACK signals transmitted by
a specific transmitting side among a plurality of ACK/NACK signals
are transmitted through a plurality of time-frequency domains.
FIG. 5 shows an example that a time-frequency diversity gain is
obtained in a manner that ACK/NACK signals for a specific UE are
transmitted across two different time-frequency domains.
In particular, ACK/NACK signals for UEs 1 to N/4 are transmitted
via a time-frequency domain placed in a left upper part of FIG. 5
and a time-frequency domain placed in a right lower part of FIG. 5,
while ACK/NACK signals for UEs N/4+1 to N/2 are transmitted via a
time-frequency domain placed in a left lower part of FIG. 5 and a
time-frequency domain placed in a right upper part of FIG. 5.
In particular, ACK/NACK signals for a specific UE in the example
shown in FIG. 5 are transmitted across two time-frequency domains.
Different ACK/NACK signals are multiplexed by CDMA within each of
the time-frequency domains and then transmitted.
Moreover, eighteen ACK/NACK signals can be transmitted via
orthogonal codes corresponding to 18 (=3.times.6) chip length
across three OFDM symbols and six subcarriers within each of the
time-frequency domains. Since two orthogonal phases are usable for
QPSK transmission, it is able to transmit 36 different ACK/NACK
signals amounting to a double of the former ACK/NACK signals.
In the example shown in FIG. 5, it is able to discriminate ACK/NACK
signals transmitted via different time-frequency domains for a
specific UE from other ACK/NACK signals using the same orthogonal
code. Yet, a diversity gain can be obtained by multiplexing the
ACK/NACK signals within each of the time-frequency domains using
different orthogonal codes.
Moreover, in the example shown in FIG. 5, in case that orthogonal
codes are specified with reference to in the size of the entire
time-frequency domains instead of specifying orthogonal codes with
reference to in the size of each time-frequency domain, it is able
to transmit more ACK/NACK signals simultaneously.
In particular, by specifying orthogonal codes not for chip length
constructed with three symbols and six subcarriers included in each
of the time-frequency domains but for 72 chip length constructed
with total six OFDM symbols and 12 subcarriers, it is able to
transmit more ACK/NACK signals simultaneously.
In the above-explained embodiments shown in FIGS. 1 to 5, a 1-bit
control signal such as an ACK/NACK signal is transmitted by
spreading in 3 or 6 OFDM symbol zones by CDMA for example. Yet, an
OFDM symbol zone usable for transmission of 1-bit control signal
such as ACK/NACK signal can include at least one or more OFDM
symbols.
Among the 1-bit control signal (ACK/NACK signal) transmitting
methods according to the above-explained embodiments of the present
invention, the method of transmitting ACK/NACK signals repeatedly
in a plurality of time-frequency domains to secure the transmission
diversity gain can be diversified in accordance with a number of
available OFDM symbol zones. In the following description, a method
of transmitting ACK/NACK efficiently in accordance with a number of
OFDM symbols used for the ACK/NACK signal transmission is
described.
FIG. 6 is a diagram for explaining a method of transmitting
ACK/NACK in case of using 1 OFDM symbol zone for ACK/NACK
transmission according to one embodiment of the present
invention.
In detail, FIG. 6 shows that four ACK/NACK signals are spread at a
spreading factor (SF) 4 in 1 OFDM symbol zone, multiplexed by CDMA
and then transmitted. In FIG. 6, a single box indicates a single
subcarrier zone. And, A.sub.ij indicates an ACK/NACK signal
multiplexed by CDMA. In this case, `i` is an index of a spread and
multiplexed signal and `j` is an index indicating a group of the
multiplexed ACK/NACK signal. An ACK/NACK group indicates a set of
the multiplexed ACK/NACK signals. And, a plurality of ACK/NACK
groups can exist in accordance with necessity of each system and a
resource situation. For clarity and convenience, FIG. 6 assumes
that there exists a single ACK/NACK group only.
Since the present embodiment assumes a case that a single OFDM
symbol is used for ACK/NACK transmission only, it is unable to
obtain a diversity gain on a time axis for ACK/NACK signal
transmission.
Yet, to obtain a diversity gain on a frequency axis, ACK/NACK
signals multiplexed on the frequency axis by CDMA can be repeatedly
transmitted in different frequency domains.
FIG. 6 shows an example that ACK/NACK signals multiplexed by CDMA
are four times repeated in different frequency domains. In this
case, the four times repetition is just an example to obtain
diversity. A count of repetitions can vary in accordance with a
channel status and a resource situation of system. In FIG. 6, each
of the four times repeated ACK/NACK signals has the same indices
(i, j) for emphasizing the repetition of the signals. But, each of
the four times repeated ACK/NACK signals can be multiplexed by
different orthogonal code or like, so in this case, these signals
can be a different signal to each other. But, for convenience of
explanation, this possibility of differentiation of each repeated
signal will be ignored in the whole context.
FIG. 6 deals with a case that a single OFDM symbols is used for
ACK/NACK transmission. The case of using a single OFDM symbols is
just an example for describing the present invention. And, the
present invention is applicable to a case of using a plurality of
OFDM symbols as well.
In more particularly, in case that ACK/NACK is transmitted via
several OFDM symbols, repetition on a time axis is also applicable
as well as a repetition on a frequency axis in order to obtain
additional diversity as well as transmitting antenna diversity.
In the following description, a case of using a plurality of OFDM
symbols for ACK/NACK signal transmission is described.
In case that OFDM symbols for ACK/NACK transmission are
incremented, it is able to use ACK/NACK signals in case of using a
single OFDM symbol for ACK/NACK transmission can be repeatedly used
for the incremented OFDM symbols intactly. In this case, since the
OFDM symbols used for the ACK/NACK transmission are incremented, it
is able to more power of a signal used for the ACK/NACK
transmission. Hence, it is able to transmit the ACK/NACK signals to
a wider area of a cell.
FIG. 7 is a diagram for explaining a method of transmitting
ACK/NACK in case of using at least 2 OFDM symbol zones for ACK/NACK
transmission according to one embodiment of the present
invention.
FIG. 7 shows an ACK/NACK signal transmitting method when a number
of OFDM symbols for ACK/NACK signal transmission is incremented
into 2, in transmitting ACK/NACK signals having the same spreading
factor as FIG. 6. In particular, FIG. 7 shows a case that a
structure in using a single OFDM symbol for ACK/NACK transmission
like FIG. 6 is intactly and repeatedly applied to a second OFDM
symbol.
In case of the transmission with the above structure, even if a
symbol number is incremented, the number of transmittable ACK/NACK
signals is equal to that of the case of using a single OFDM symbol.
This is because more time-frequency resources are used for the
transmission of the same number of ACK/NACK signals by
substantially incrementing the time-frequency repetition count as
more OFDM symbols are used for the ACK/NACK signals repeated on the
frequency axis only in case of using a single OFDM symbol only.
In case of performing the transmission by this method, more power
can be allocated to the ACK/NACK transmission but waste or resource
may take place. In case that more OFDM symbols are used for the
ACK/NACK signal transmission to reduce the waste of resource, if a
transmission is performed by decrementing the repetition count on
the frequency axis per the OFDM symbol, the same time-frequency
domain as the case of using a single OFDM symbol can be occupied.
Hence, it is able to utilize resources more efficiently.
FIG. 8 is a diagram for explaining a method of transmitting
ACK/NACK in case of using at least 2 OFDM symbol zones for ACK/NACK
transmission according to one preferred embodiment of the present
invention.
FIG. 8 shows an example that resources are more efficiently
utilized by decrementing a frequency axis repetition count of
ACK/NACK signals multiplexed by CDMA in case that the number of
OFDM symbols for ACK/NACK signal transmission are incremented into
two.
Although ACK/NACK signals are repeated twice compared to four times
in FIG. 6, as the number of OFDM symbols used for the ACK/NACK
signal transmission is incremented, the use of four time-frequency
resource domains is the same as the case of using a single OFDM
symbol.
Compared to FIG. 7 which shows the case of performing transmission
by applying the same ACK/NACK signal structure to the entire OFDM
symbols, assuming that the same time-frequency resource is used,
FIG. 8 shows that ACK/NACK signal transmission is possible twice.
Hence, resources can be more efficiently used.
Comparing to FIG. 7, since the number of, time-frequency resource
domains used for the ACK/NACK signal transmission is decremented, a
signal power for the ACK/NACK signal transmission may become less.
Yet, since the overall ACK/NACK signals are transmitted across the
time-frequency domain, more efficient transmission power allocation
per symbol is possible rather than the case of transmitting the
ACK/NACK signals using a single OFDM symbol only.
Referring to FIG. 8, when a plurality of OFDM symbol zones are used
for ACK/NACK transmission, in case that the method of transmitting
a specific ACK/NACK signal via a different frequency domain in each
OFDM symbol zone according to the present embodiment is taken, it
is more advantageous that power allocation to each ACK/NACK signal
can be carried out more flexibly rather than the method of
transmitting ACK/NACK via different frequency domains within each
OFDM symbol zone. This is explained in detail with reference to
FIG. 9 as follows.
FIG. 9 is a diagram to explain a principle that power allocation
flexibility is increased in case of transmitting ACK/NACK signals
by the embodiment shown in FIG. 8.
In (a) and (b) of FIG. 9, A.sub.1, A.sub.2, A.sub.3 and A.sub.4
indicate ACK/NACK signal groups multiplexed by CDMA, respectively.
In particular, (a) of FIG. 9 shows a format that CDMA-multiplexed
ACK/NACK signals are transmitted by being repeated in different
frequency domains within a same symbol zone. And, (b) of FIG. 9
shows a format that CDMA-multiplexed ACK/NACK signals of the
present embodiment are transmitted by being repeated in different
frequency domains within different OFDM symbol zones,
respectively.
In case that ACK/NACK signals are transmitted in a same manner
shown in (a) of FIG. 9, total powers allocated to the respective
OFDM symbol zones should be allocated by being distributed to two
ACK/NACK signals. On the contrary, in case that ACK/NACK signals
are transmitted in a same manner shown in (b) of FIG. 9, total
powers allocated to the respective OFDM symbol zones can be
allocated by being distributed to four ACK/NACK signals. Hence,
flexibility of power allocation can be enhanced more than that of
the case shown in (a) of FIG. 9.
In other words, when the number of OFDM symbol zones available for
ACK/NACK transmission is plural like the present embodiment, in
case that ACK/NACK signals are transmitted via different frequency
domains in different OFDM symbols, flexibility in power allocation
is enhanced to diversify power allocation for ACK/NACK signals per
a user.
In the above-explained embodiment of the present invention, a
spreading factor for multiplexing of a plurality of ACK/NACK
signals, a repetition count in time-frequency domain, and the
number of OFDM symbols for ACK/NACK signal transmission are just
exemplary for the accurate explanation of the present invention but
other spreading factors, other repetition counts and various
numbers of OFDM symbols are applicable to the present
invention.
In the above-described example for explaining the present invention
in accordance with the time-frequency resource, a case of using a
single transmitting antenna that does not use transmitting antenna
diversity is represented only. Alternatively, the present invention
is also applicable to the case of using a two transmitting antennas
diversity scheme or a four transmitting antennas diversity
scheme.
It is apparent to those skilled in the art that the above-explained
scheme for obtaining the time-frequency diversity gain from the
ACK/NACK signal transmission can be used side by side with the
scheme of using FDMA or TDMA as well as the case of using CDMA for
the multiplexing of different ACK/NACK signals according to one
embodiment of the present invention.
The above-explained multiplexing and transmission schemes of
ACK/NACK signals are identically applicable to the multiplexing and
transmission scheme of a plurality of power control signals
transmitted to different UEs in downlink. Particularly, a downlink
ACK/NACK signal and a downlink power control signal can be
transmitted by being multiplexed in the same time-frequency domain
by CDMA.
Moreover, the above-explained ACK/NACK signal multiplexing and
transmission schemes are identically applicable to uplink ACK/NACK
signal transmission for data packets transmitted in downlink as
well.
Moreover, if the number of OFDM symbols used for transmission of
ACK/NACK signal can be variable in a specific system, it is
preferable that the number of repetition of ACK/NACK signal is
decreased in accordance with the increase of the OFDM symbols
used.
INDUSTRIAL APPLICABILITY
According to one embodiment of the present invention, in
multiplexing a plurality of 1-bit control signals, a plurality of
control signals of a specific UE can be transmitted via orthogonal
or pseudo-orthogonal codes differing from each other using CDMA
mainly. Hence, the present invention enhances reliability on a
corresponding control signal transmission.
And, frequency and/or time diversity can be obtained by carrying
out FDMA and/or TDMA on the 1-bit control signal transmission side
by side and by distributing to transmit a plurality of control
signals for a specific UE on each time-frequency domain.
Moreover, in case of transmitting the 1-bit control signal through
a plurality of time-frequency domains, by specifying to use an
orthogonal code used for transmission in accordance with the size
of the whole time-frequency domains instead of in the size of each
time-frequency domain, it is able to increment a number of control
signals that can be simultaneously transmitted.
Besides, in case that a plurality of OFDM symbols are used for
1-bit control signal transmission, by transmitting a CDMA modulated
1-bit control signal on a different OFDM symbol area through a
different frequency domain, it is able to perform efficient
transmission in aspects of resource efficiency and diversity gain.
And, it is also able to make a power allocation more flexible
within each OFDM symbol area.
Accordingly, a control information transmitting method according to
the present invention has a configuration suitable to be applied to
3GPP LTE system. Moreover, a control information transmitting
method according to the present invention is applicable to random
communication systems that require specifications for a control
information transmission format in time-frequency domain as well as
to the 3GPP LTE system.
While the present invention has been described and illustrated
herein with reference to the preferred embodiments thereof, it will
be apparent to those skilled in the art that various modifications
and variations can be made therein without departing from the
spirit and scope of the invention. Thus, it is intended that the
present invention covers the modifications and variations of this
invention that come within the scope of the appended claims and
their equivalents.
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